NA TURE 



573 



THURSDAY, OCTOBER 13, 1904. 



(ECOLOGICAL PLANT-GEOGRAPHY. 

 Plant-Geography upon a Physiological Basis. By Dr. 

 A. F. W. Schimper. Translated by W. R. 

 Fisher, B.A. Revised and edited by Percy Groom, 

 M.A., D.Sc, F.L.S., and I. Bayley Balfour, M.A., 

 M.D., F.R.S. Pp. XXX + 839. (Oxford : University 

 Press, 1903.) Price 42^. net. 



WE welcome most heartily the appearance of 

 this translation of Schimper's great work, 

 " Pflanzen-Geographie auf physiologischer Grund- 

 lage," and the more so as it stands alone in being 

 the only comprehensive' work on oecological plant- 

 geography in the English language. 



The beginnings and gradual development of the 

 study of oecology may be traced during the course of 

 the last century in the writings of Humboldt, the 

 De CandoUes, Darwin, Grisebach, Drude, Kerner, 

 Engler, and others. A new phase was marked by the 

 appearance in 1896 of Warming's " Lehrbuch der 

 okologischen Pffanzen-Geographie " (the original 

 Danish edition was published in 1S95), and in 1898 of 

 the larger work of Schimper. The latter, which forms 

 the subject of this notice, possesses a wealth of well 

 chosen illustrations absent from the text-book of 

 Warming. But even these later works are, in spite 

 of the undoubted advance which they mark, to be re- 

 garded largely as pioneers, for, to quote from the 

 author's preface to the book before us : — 



" A satisfactory general survey of oecological plant- 

 distribution cannot be attempted with the material at 

 present available. This book is therefore chiefly of a 

 tentative nature, and attempts by a precise statement 

 of pending questions to stimulate further research." 



The work is divided into three parts. In the first 

 (pp. 1-156) the various factors affecting plant-life are 

 considered. The second (pp. 159-206) discusses the 

 arrangement of vegetation into " formations " and 

 " guilds "; while the third and largest part (pp. 209- 

 839) is less general, and is largely occupied with a 

 description of the vegetation of the zones and regions, 

 thermal and other, into which the surface of the earth 

 may be divided. 



At the outset the author emphasises the fact that 

 " the characteristics of organisms are physiological," 

 and this application of the principles of physiologj' to 

 the problems of morphology and distribution forms the 

 idea underlying the whole of the book. 



In addition to the generally accepted classes of 

 " hygrophytcs " and " xerophytes," Schimper recog- 

 nises a third or intermediate tvpe, which he calls 

 " tropophytes." Under the latter term are included 

 " all plants whose conditions of life are, according to 

 the seasons of the year, alternately those of hygro- 

 phytes and xerophytes." Good examples of this class 

 are our deciduous trees ; these possess hygrophilous 

 leaves, which are shed periodically, while the axes and 

 buds, which alone are called upon to endure the 

 >hysiologically dry " conditions of winter, are dis- 

 tuictly xerophilous in character. Warming's class of 

 •' niesophytes," or plants adapted to medium conditions 

 NO. 1824, VOL. 70] 



as regards moisture, was a convenient one, but the 

 term " tropophytes " is to be preferred, as it directs 

 attention to the physiological significance of many 

 adaptations correlated with an alternation of wet and 

 either dry or cold seasons. 



Just as humidity is the dominant factor in deter- 

 mining the form of plants, so temperature plays the 

 most important part in their distribution. The 

 oecological importance of light, in spite of its powerful 

 influence on the form and life of plants, is, according 

 to the author, less than that of heat and rainfall, be- 

 cause the amount of light in different climatic regions 

 is less variable than is the supply of the other two 

 factors. 



The remaining chapters of part i. are devoted to a 

 discussion of the air, the soil, and animals as oecological 

 factors. 



In part ii., under the heading of " Formations and 

 Guilds," the conditions which determine the differenti- 

 ation of the earth's vegetation are dealt with. Accord- 

 ing to Schimper there are three controlling factors — 

 the type of " vegetation " in the tropical and temperate 

 zones is determined by the climatic humidity ; the type 

 of the " flora," especially as regards the larger 

 systematic groups, is, so far at least as existing factors 

 are concerned, dependent primarily on heat; while " the 

 soil as a rule merely picks out and blends the material 

 supplied by these two climatic factors, and on its own 

 account adds a few details." 



Two oecological groups of " formations " are dis- 

 tinguished : — (i) "climatic or district formations, the 

 character of whose vegetation is governed by atmo- 

 spheric precipitations " — these include three main 

 types, woodland, grassland, and deserts — and (2) 

 " edaphic or local formations, whose vegetation is 

 chiefly determined by the nature of the soil"; such 

 edaphic formations are moors, swamps, sand-dunes, 

 &c. This grouping is an excellent one, but some will 

 regret the use by the author of the term " formations " ; 

 admittedly it is difficult of definition, but as used here 

 the term is unnecessarily wide, and includes groups of 

 very unequal value. Another objection to its use is 

 the fact that it has been employed by different authors 

 in a variety of senses. Perhaps it would have been 

 better to have followed the usage of Warming in the 

 work cited above, and applied the term "vegetation " 

 to the larger groups such as woodland, grassland, &c. ; 

 while for the smaller local ones, which are characterised 

 by the presence of one or more dominant species, 

 " plant-associations " (" Pflanzenvereine ") could per- 

 haps have hardly been improved upon. 



Part iii. contains a masterly description of the vege- 

 tation of the globe from the cEcological point of view. 

 The primary division is into "zones," dependent on 

 temperature, i.e. tropical, temperate, and arctic, and 

 these occupy respectively the first three of the five 

 sections which make up this part of the work. Each 

 section begins with a general discussion of the 

 characters of the climate of the particular zone under 

 consideration, and stress is laid on the fact that periodic 

 phenomena, or alternations of rest and activity in the 

 functions of plants, occur as generally, though less 

 obviously, in tropical as in temperate climates. Some 



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